Lecture 21 (Topology)

A topological space (X, τ) is called disconnected if there exist U, V ∈ τ such that U ∪ V = X, U ∩ V = ∅, and:

1. A.Both U and V are nonempty
2. B.U is finite and V is infinite
3. C.U is the complement of V in some larger space
4. D.U and V are also closed in some other topology